The invention relates to a device for binding objects, such as cable bundles, which has a toothed strap and a lock fixed to one end of the strap.
It is based on known devices (EP-A-75 501) which comprise a toothed strap and a lock which is fixed to one end of the strap and has a strap opening for accommodating and securing the free strap end. The strap is guided into the strap opening from that side of the lock which is directed toward the object which is to be bound, and is tensioned from the other side. If the encircled object has a circular boundary in cross section, the strap follows the circular boundary and approaches the lock tangentially. If the diameter is large, the two strap ends approach the lock more or less from opposite sides. It is only in the case of objects having very small dimensions that the angle can drop to 90xc2x0 or even below. Before the free strap end runs into the strap opening of the lock, it will thus first of all be positioned on a surface of the lock which is directed toward the object which is to be bound, this surface being referred to hereinbelow as the strap-guiding surface. Following this strap-guiding surface, the strap is deflected in the direction of the strap opening. In the case of known cable-binding devices, this is the bottom edge of the lock which is reached first of all by the free strap end.
When the strap is tensioned, it is necessary to overcome the friction which acts, on the one hand, between the strap and the lock (mainly in the region of the deflection of the strap) and, on the other hand, between the strap and the object which is to be bound. This friction may differ to a fair extent from case to case. This has a disruptive effect on the effort of producing a predetermined tensioning in the strap part encircling the object as a result of determining the tensioning force. The friction to which the surface of the object which is to be bound is subjected by the strap, said friction differing from case to case, may also affect the strap tensioning. Also regarded as being disadvantageous is the fact that the act of the strap being tensioned sliding over the surface of the object which is to be bound may damage the surface of the object (for example cable insulations).
The invention eliminates or moderates these disadvantages. Provision is accordingly made for the side borders of the strap-guiding surface to be provided with raised border ridges. This results in the latter forming a lateral guide for the strap moved over the guiding surface. This ensures that the strap reaches the deflecting surface, which deflects the strap into the strap opening following the strap-guiding surface, precisely perpendicularly to the axis of curvature of said deflecting surface. This is because the invention has found that a reason for different frictional forces between the strap and lock resides in the fact that the strap sometimes runs askew into the lock.
Furthermore, the raised side borders of the strap-guiding surface form an additional support, alongside the strap, for the surface of the object which is to be bound. This means that the force by which the strap, during its movement relative to the surface of the object which is to be bound, butts against said surface are reduced, as a result of which the risk of damage is also reduced.
The lateral-guide function of the border ridges requires the distance between the latter not to exceed the width of the strap to any significant extent. Normally, the distance between them should exceed the width of the straps by no more than 10%. A distance of around 3 to 7% above the width of the strap is preferred.
The height of the border ridges above the guiding surface in order for said border ridges to provide an effective support in relation to the surface of the object depends on the compliance of the object. The more flexible is the object, the smaller is the height required for the border ridges. For binding devices which serve for binding cable harnesses, it has proven successful if the greatest height of the border ridges above the guiding surface is at least half the thickness of the strap. In this context, it is expedient if, on the side of the strap which is to be directed toward the object which is to be bound, the borders of the strap are provided with a rounding or bevelling, of which the width, as seen from each side, is equal to at least approximately half the strap thickness.
The invention has found that, in order to reduce the friction between the strap and the lock, it is expedient for the strap to pass in the direction of the strap opening by way of the largest possible radius of curvature. The strap-guiding surface should thus pass into the surface of the strap opening by way of a curvature, of which the radius is equal to at least half the strap thickness.
The strap-guiding surface is preferably elongate and encloses an obtuse angle with the direction of the strap opening, said obtuse angle expediently being greater than 110, and further preferably being greater than 120xc2x0.
Good results can be achieved by a strap-guiding surface which runs approximately rectilinearly in longitudinal section.
The strap-guiding surface, in relation to the object which is to be bound, should assume a direction which corresponds to the direction of the strap running toward the lock, that is to say approximately a circumferential or tangential direction. This requires a certain alignment of this surface with that region in which the other strap end is fixed to the lock. The direction of the strap-guiding surface is preferably aligned with this region. If the center point of this region is defined as the point of intersection between the center line of the strap extending from the lock in the non-tensioned state and the center line of the wall on which the strap is fastened integrally, the direction of a significant part of the strap-guiding surface should be aligned with this point, that is to say the extension of the strap-guiding surface should run past said point at a distance which is no greater than half the strap thickness.